Improvement in pneumatic signal apparatus for railways



W.-E. PRALL.

PNEUMATIC SIGNAL APPARATUS FOR RAILWAYS. No. 17'ZA90. v PatentedJan.18,1876.

N.FETERS. PHOTO-UTHOGRAPHER. WASHINGTON, D C

UNITED STATES WILLIAM E. PRALL, OF WASHINGTON, D. 0., ASSIGNOR TO PRALLRAILVVAY- PATENT QFrIcE;

SIGNAL AND TELEGRAPH COMPANY, OF NEW YORK, N. Y.

- IMPROVEMENT IN PNEUMATIC SlGNAL APPARATUS FOR RAILW'AVS.

Specification forming part of Letters Patent No. 172,490. dated January18, 1876; application filed September 1,1 s14.

OAsE G. i

To all whom it may concern:

Be it known that I, WILLIAM E. PRALL, of-

Washington city, District of Columbia, have invented Improvements inApparatus for Pneumatic Signal Apparatus for Railways, of.

which the following is a specification: 1 My invention relates to thesystem of operating signals for railroads by the use of compressed air,which I have described in the specifications of Letters Patent of theUnited States heretofore granted to meand in appliply of:air, at thehighest pressure, in the main,

andretainthe same independently of variations'of pressure inthe latter.D is a supply tank, connected eitherwith the main A or with the tank Bby means of a pipe, E, controlled by ,a cock or valve, F. G is a pistonor plunger working in a chamber or cylinder, H, and loaded with one ormore weights, I. H is an upper bearing for the piston-rod. J is a smallpipe leading from the tank D to the space in the chamber H beneath thepiston G. This pipe J may be dispensed with by causing thepiston-chamber to open at its lower or front end either directly intothe tank D, or into the pipe E above the cock F. The piston G isarranged (as shown in the drawing) to actuate a lever opening andclosing the cock F, so that when the piston is forced up by the pressureof air admitted thereto its movement will operate to shut the cock andclose the pipe E, and thusinvariably cut off the further admission ofair to the tank D, whenever the pressure of that already admittedcounter-balances the weights I. When the pressure in the tank so fardiminishes again as to permit the piston to move under the influence ofthe weights, its movement will open the cock and admit more air.

a fixed standard in the tank D, for use in signaling, irrespective ofthe pressure in the airlnain, so long as the pressure in the main itselfdoes not fall below such standard.

The piston may be made to work horizontally instead of vertically, andsprings belsubstituted for the weights I, and a diaphragm may in allcases be employed as an equivalent for a piston, G. i

-K is an aircommutator, consisting substantiallyof a valve, to,controlling an aperture between an upper and lower chamber, 1)

b, and to which is suspended a weight, 0. The

air supply pipe communicates with the lower chamber b, and theair-delivery pipe with the upper chamber 1). The valve is kept closed,and the weight uplifted, by the pressure of the air from the supply-pipebearing against itsv under surface. The valve is forced open whendesired by the movement of a cam, d, secured upon the end of a rockingshaft, and which bears in a yoke upon the upper endof a rod, projectingfrom the valve upward and outward After the valve has been through thecase. opened it is kept open by the weight 0 until the outward pressurein the upper chamber, upon the transverse area of the. rod projectingoutwardly therefrom, becomes sufficient to carry up the valve andweight.

the commutator K to the. signals connected therewith. That portion, M,of the signalpipe adjacent to the commutator is enlarged, so as to be ofa larger capacity than its supply-pipe, in order to avoid or preventsuch a momentary accumulation of pressure in the signalpipe, at themouth of the commutator-- consequent upon the sudden admission of theair thereto-as would operate to close the valve prematurely. Therelative proportions of the supply and signal pipes, adjacent to thecommutator, may be determined by means of a cock, L, placed in thesupply-pipe. This cock L serves likewise to adjust and control theadmission'of air to the supply-pipe, and thus determine the interval oftime during By this means ,a constant air-pressure may be maintainedat MM is the signal or delivery pipe carrying air from,

which the commutator-valve shall remain open before automaticallyclosing. N is an airta'nk' combined with the enlarged portion M of thesignal-pipe M M to permit a more full and free. discharge of air throughthe commutator into the signal-pipe before the commutator-valve closes,by reason of an accumulation of pressure in said pipe.

P is an exhaust cock or valve placed in the signal-pipe M to provide fora full, free, and rapid discharge of air therefrom, when required. P isa lever, connected with the cock, and arranged to be struck (when thecock is closed) by an attachment upon the locomotive or cars of apassing train, and to thereby operate to throw open the said cock. P isa second lever connected with the cock, and arranged to be drawn up whenthecockis opened, and to operate when thrown down (as shown in thedrawing) to close the same. R is an air piston or plunger working in asuitable chamber or cylinder, and provided with a rod, R, projectingoutwardly from said chamber. A bar, S, slotted at its lower end to en- 5gage a pin in the valve-lever P is secured toan arm, T, which projectsfrom the rod R, and the slot in the bar S is so extended as that anupward movement of the piston, arm,

and bar will not move the lever P but when signal pipe, M, a valve orcook controlling said lever is elevated by the opening of the cock P itspin will bear against the upper end of the slot, so that the descent ofthe piston will operate to forcedown the lever and close the cock. W isa pipe connecting the signalpipe MM with the pistonichamber beneath thepiston, so that when. airis admitted to the sig nal-pipe the piston willrise.

should be of less capacity than the signal- This pipe W pipe M and itsexhaust-vent, in order that the piston may not descend and close theexhaust cook or valveuntil the compressed air in the signal-pipe isfully discharged. The

proper degree of contraction in the pipe W,

with-reference to the pipe M and its exhaustvent, may, however, best beadjusted and determined by placing a cook or valve, X, in said pipe W;or a check-valve opening freely toward the piston-chamber, butwhich,.when

closed, will present a contracted orifice for the return of the air, maybe employed in said pipe as a substitute for its contraction otherwise.I contemplate, also, as an equivalent device, placinga check-valve inpipe W,so

as to admit air to the piston-cylinder, but pre vent entirely itsreturn, and combining a separate exhaust-valve with the piston-chamberin such manner as that it shall be opened and closed simultaneouslywitht-he main exhaustvalve P by the movement of the bar S, the object ofthese devices being to providefor an exhaust of air from thepiston-chamber, which shall be produced simultaneously with the exhaustof air from the signal-pipe, but which shall be so adjusted, controlled,and retarded as that the piston will not move by reason of such exhaustto-close the main exhaust-valve P until the air in the signalfpipe isfully discharged. Y is a strainer to'protect the valves from dirt.

I claim as my invention- 1. In combination with each other an airtank,D, a pipe to supply the same, a cook or valve to govern saidpipe, and apiston, G, actuating the cock and subjected to the pressure of air inthe tank, substantially as and ;for the purpose herein set forth.

2. The combination, with an automatic air valve orcommutator, K, andwithits airs'upply pipe,.of a delivery-pipe, M,'having larger capacitythan said supply-pipe, substantially as and for the purpose herein setforth. 3. In combination with each other an airan exhaust-vent in saidpipe, and a weighted :piston, R, actuated and supported by the :pressureof air admitted thereto from the pipe M, and operating automatically,when relieved. 'from such air-pressure, to close said exhaustvalve,substantially in the manner and forthe purpose heroin set forth. v

4. The combination, with an exhaust-vent; and valve, P, in anair-pipe,M, and with a piston, R, actuated by compressed air from Esaidpipe, and operating, when relieved'frompressure, to close said valve, ofa cockor valve, X, controlling the communication between :the air-pipeand piston to insure a comparatively slow discharge of air from thepistonchamber, when the exhaust-vent in the airpipe is opened,substantially as and for the purpose herein set'forth.

W. E. PRALL. Witnesses:

R. E. SHAPLEY,

DAVID A. BURR.

